It's a dungeon-like place that consists of a single floor that is lower than the other locations in Riley's mind, and is closed off by a giant door. Frank and Dave serve as two Subconscious guards in front of the door.
Its purpose is to lock up and confine troublemakers. Because of this, it houses Riley's greatest fears, which appear as an exaggerated allegory. Such include a broccoli-like forest, the staircase leading to the basement, her grandmother's vacuum cleaner, or the worst fear of all, Jangles the Clown.
After Bing Bong is arrested, he is imprisoned in Riley's Subconscious. However, Joy and Sadness allow themselves to be captured in order to enter inside and rescue Bing Bong. They also free Jangles, lead him to Dream Productions, and use him to wake up a sleeping Riley, so they can ride the Train of Thought back to Headquarters.